Method and system for estimating the forces and torques generated by the contact of a tire with the road in an instrumented wheel

Abstract

The invention relates to a method for measuring the forces and the moments generated by the tire-road contact from the combination of unit deformation or strain signals measured in different angular and radial positions of the wheel. The angular positions in which the sensors are placed are those permitted by the geometry of the tire. The combination of deformation signals results in six or more signals that are independent of the angular position of the measuring sensors with respect to the tire-road contact point. The effect of temperature and loads that generate deformation signals that do not depend on said angular position of the measuring points, such as centrifugal forces, have been eliminated from the aforementioned signals. Said signals provide estimates of the loads by means of the resolution of two systems of linear equations with constant matrices and three unknowns each.

The invention claimed is: 
     
       1. Method for estimating the forces and torques generated by the contact of the tire with the road comprising:
 obtaining deformation signals in a plurality of measuring points of a wheel having a tire mounted thereon by means of a plurality of deformation sensors; 
 processing the deformation signals as force signals and as moment signals generated at the measuring point; 
 wherein the measuring points are distributed by following at least three concentric measuring circumferences with respect to the center of the wheel, with at least five measuring points distributed equidistantly for each measuring circumference; 
 and the processing of the signals comprises a combination of the deformation signals of the sensors grouped in the same circumference to decouple the signal resulting from the angular position of the sensors. 
 
     
     
       2. Method according to  claim 1 , wherein the deformation signals are decomposed in three perpendicular axes, the X axis being the movement direction axis, the Z axis being the direction axis perpendicular to the contact surface, and the Y axis being the direction axis perpendicular to the surface of the wheel. 
     
     
       3. Method according to  claim 2 , wherein the deformation signals are combined in such a way that the symmetrical components according to the X direction of the moment M x , and according to the Y and Z direction of the forces F y  and F z , do not depend on the antisymmetrical components according to the X direction of the Force F x  and according to the Y and Z directions of the moments M y  and M z  in a substantial manner. 
     
     
       4. Method according to  claim 3 , wherein the combined deformation signals comprise a first resulting signal, E iS , which depends on the symmetrical components of the measuring circumference (i), with information from the first harmonic. 
     
     
       5. Method according to  claim 4 , wherein the first resulting signal E iS  is calculated for at least three measuring circumferences. 
     
     
       6. Method according to  claim 3 , wherein the combined signals comprise a second resulting signal, E iA , which depends on the antisymmetrical components of the measuring circumference (i), with information from the first harmonic. 
     
     
       7. Method according to  claim 6 , wherein the second resulting signal E iA  is calculated for at least two measuring circumferences. 
     
     
       8. Method according to  claim 3 , wherein the combined signals comprise a third resulting signal, E′ iA , which depends on the antisymmetrical components of the measuring circumference (i), with information from the second harmonic. 
     
     
       9. Method according to  claim 8 , wherein the resulting signal E′ iA  is calculated for at least one measuring circumference. 
     
     
       10. Method according to  claim 1 , further comprising modeling the wheel and the tire to obtain a coefficient matrix related to the amplitude of the harmonics of the influence functions, where the influence functions present the unit deformation or strain generated at said point when the force or torque under consideration has a unit value and the rest have a null value. 
     
     
       11. Method according to  claim 1 , wherein the deformation sensors are placed in the radial direction. 
     
     
       12. Method according to  claim 1 , wherein the deformation sensors are strain gauges. 
     
     
       13. System for estimating the forces and the torques generated by the contact of a tire with the road that comprises:
 a plurality of deformation sensors installed in the wheel having the tire mounted thereon, said sensors being configured to obtain the deformation signal in a plurality of measuring points, 
 processing means of the deformation signals as force signals and as moment signals generated at each measuring point, 
 wherein the deformation sensors are distributed by following measuring points along the length of at least three concentric measuring circumferences with respect to the center of the wheel and with at least five measuring points distributed equidistantly for each measuring circumference; 
 and the processing means of the signals are configured to combine the deformation signals of the sensors grouped in the same circumference such that the resulting signal does not depend on the angular position of the sensors. 
 
     
     
       14. System according to  claim 13 , wherein it comprises the wheel where the plurality of sensors is installed. 
     
     
       15. System according to  claim 13 , wherein the deformation sensors are placed in the radial direction. 
     
     
       16. System according  claim 13 , wherein the deformation sensors are strain gauges.